<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        let sum = 0
        let num = prompt(`请输入一个数我们将对您输入的这个是进行累加`)
        for (let i = 1; i <= num; i++) {
            sum += i
        }
        document.write(`输出结果是${sum}`)
    </script>
</body>

</html>